Electrical condenser



July 18, 1933. EN 1,918,716

ELECTRICAL CONDENSER Filed April 29, 1935 INVENTOR SAMUEL RUBEN ATTORNEY Patented July 18, 1933 UNITED STATES PATENT OFFICE SAMUEL RUBEN, OF NEW ROCHELLE, NEW YORK, ASSIGNOR T0 RUBEN CONDENSER COMPANY, OF -NEW ROCHELLE, NEW YORK, A CORPORATION OF DELAWARE ELECTRICAL Application filed April 29,

This invention relates to electrical condensers and to a method of making such devices and more particularly to such condensers which have a current blocking film on at least one electrode and a film-maintaining composition interposed between the electrodes and in physical contact with the current-blocking film.

The general object of the invention is to provide such a condenser which is compact in form and which is electrically of high efiiciency.

A specific object is the provision of a con denser of this type having a low power factor.

A further object is to rovide a condenser of this type having uni orm. characteristics and capable of bein produced at a low cost.

An additional ob ect is the provision or a condenser of this type having a fibreless spacer medium which has been rendered electrolytically conductive.

Still a further object is to provide an improved condenser of the dry or plastic electrolytic type as exemplified in my United States Letters Patent #1510973 of 23 April 1929; #1,714,191 of 21 May 1929 and #1,891,207 of 13 December 1932, which employ filmed electrodes separated by a fibrous cloth spacer impregnated wits. a viscous glycol or glycerol borate material, serving as the electrolyte.

Other objects will be apparent from the disclosure and from the drawing in which Fig. 1 is a perspective view, partly broken away, of one embodiment of the invention showing a fiat plate condenser;

Fig. 2 is a view similar to Fig. 1 showing a corrugated electrode;

Fig. 3 is a perspective view of a modification showing the arrangement of the invention in coiled form and a Fig. 4 is a vertical sectional view of an arrangement somewhat similar to Fig. 3, enclosed within a protective casing.

This application may be said to be a continuation in part of my co-pending application Serial Number 618,872 filed 23 June 1932, in which is described an electrolytic condenser employing film formed electrodes and CONDENSER 1933. Serial No. 668,596.

a cellulose spacing medium containing a conductive plasticizer.

The dry electrolytic type of condenser as described in my aforementioned patents, ofl'ers several advantages and improvements over the wet types, in relation to fundamental considerations as capacitance, electrical, chemical and physical aspects.

Basically, an electrolytic condenser must maintain a dielectric film on the anode. This requires an expenditure of energy at the anode as represented by the energy required to form and maintain the aluminum oxide film and gas layer. llhis maintenance of the oxide and gas layer is dependent upon the drop of potential between the anode and electrolyte and the current density.

"W hen the electrolyte is in a dry or plastic "form, complete maintenance of the oxide film and gas layer on the anode obtains, as due to thehigh specific resistance of the electrolyte, (in the case of a typical glycol borate electrolyte, about 1100 ohms per cm cube with a 1 h (hydrogen ion) concentration of 2.5) a limited ionization is had which allows adequate energy drop at the anode to form and maintain the capacitance film without the use of high currents. This prevents localization and afiords a uniform distribution of current over the entire anode surface. Due to the organic nature of the electrolyte suspension medium, any tendencytoward local forming andcorrosion is minimized.

The close spacing between the electrodes provides a low internal resistance and a better average power factor is obtained than with the low resistance liquid type.

The reaction product obtained by the combination of the glycol or glycerol with the borate salts affords a stable compound which allows higher and lower temperatures to be applied, due to the low vapor pressure of the compound. 7 Another factor assisting in the mechanical maintenance of the film is the low ionic mobility of the plastic electrolyte.

1n the present condenser, I have augmented these advantages.

The invention comprises an anode of film forming metal and a cooperatin cathode spaced by a sheet of a flexible non-hbrons reenerated cellulose material, such as is popufarly designated cellophane, WhlCh as been impregnated and made electrically conductive by the addition of a conductive electrolyte which may be in the form of a plastlcizer such as glycol or glycerol compounds. If the condenser is to be used for alternatlng current work, both electrodes are compose of film-forming metals.

In accordance with the present invention, a metallic electrode is formed from a sheet of film-forming material, such as aluminum, tantalum, magnesium and alloys including one of these metals, aluminum bemg preferred. This electrode sheet is provided with a current-blocking film, such as, for example, by the well known electrolytic method with the use of a sultable electrolyte, such as a borax solution. The current blocking film may then be washed, if desired, in a suitable cleansing solution, such as by passing the sheet successively through a bath of alcohol and a bath of distilled water. In some cases, it is also desirable to pass the clcaned sheet through a viscous bonding liquid to provide a thin coating whlch becomes closelv allied with the electrolyte spacer. This affords complete coverage of the anode area and prevents separation of the anode from the film-maintaining electrolyte. This viscous bonding liquid may consist of or 1nclude one or more of the polyhydric alcohols or products thereof having two or more hydroxyl radicals, such as for example, glycerine or ethylene glycol.

The cathode material is preferably aluminum, although not necessarily so. For alternating current uses, however, the cathode should be of a film forming metal, preferably a duplicate of the anode.

The electrolyte-carrying spacer is prepared by immersing the cellophane 1n a bath of the electrolyte so as to thoroughly impregnate it. Generally, it may be stated that the cellophane is made as follows: Highly purified-cellulose is mercerized with caustic soda, the resulting alkali cellulose bemg treated with carbon bisulphide to form cellulose xanthate which is dissolved in water and caustic soda to form viscose. Thin layersof viscose are coagulated by a solution of m1neral salts and the cellulose regenerated by mineral acids. The sheet is then washed, bleached and dried. For the purposes of this invention, such a sheet is then immersed in a viscous polyhydric alcohol, such as ethylene glycol or glycerine which 1s preferably somewhat acidulated and whlch may contain a small quantity of water to facilitate the impregnation. The sheet is then passed through a conductive salt bath such as an aqueous bath of ammonium borate,bor1c acld or other conductive compounds capable of being employed as an electrolyte in a condenser of the electrolytic type. The borate is drawn into the glycol or glycerol and a conductive cellulose spacer is obtained.

Another satisfactory method of rendering the cellophane conductive is to use a sheet of cellophane which may or may not have been previously softened by glycol or glycerol impregnation and pass it throu h a hot glycol-borate solution, or other con uctive glycol or glycerol compound.

Still another method is to introduce the conductive salts into the viscose or at a later stage in the manufacture of the cellophane.

In the prior condensers of the dry or plastic type, the electrolyte contacted the electrodes through the spaces in the gauze or by conduction along and through the cotton fibres of the gauze. In the spacer of the present invention, which is relatively non porous in comparison with the reticular gauze spacer, conduction occurs through impregn ation of the minute intercellular spaces or pores of the cellophane, not visible to the naked eye. There may also be conduction through intercellular chemical transference.

There is no conduction through fibres as the material is non-fibrous.

In the construction of the condenser, the conductive cellophane spacer is placed between the anode and cathode and compressed to insure good physical contact. If the condenser is to be rolled, another layer of the impregnated cellophane is placed over the cathode and the rolling carried out in the usual manner.

Such a condenser has a very uniform distribution of current over the entire contacting area and localization is prevented. The impregnated cellophane spacer serves to allow operation at higher voltages than heretofore permissible in electrolytic condensers and I have been able to operate the present condensers at voltages in excess of 600 volts without localization of current discharge through the condenser or sparking. Should sparking occur, due to an over Volta e, carbonization does not readil occur, ecausc there are no conductive bres in contact with the anode, as would be the case if a fibrous spacer such as gauze or paper were used. Furthermore, separation of the fibres and non-uniform conduction, which would occur through the use of an impregnated paper spacer, are avoided.

While this conductive cellophane spacer may have its largest ap lication in condensers of the dry or plastic type, I have found that it can be used to advantage in electrolytic condensers of the wet type. As thus used, it would allow a much closer s acing of the electrodes than has been hereto ore practicable, the spacer being wound between the two electrodes and immersed into the electrolyte solution, such as the aqueous boric acid or acidified ammonium borate solutions or other electrolytic solutions commonly used in electrolytic condensers. When used in a wet condenser, the cellophane may first be treated with glycerine or ethylene glycol or glycerol or glycol borate to render it conductive.

lVhere it is desirable to provide a hot impregnated type of condenser, one of the electrodes, preferably the anode, can be corrugated. In such case, the cellophane is rolled between the two electrodes into condenser form and the rolled condenser placed in a hot solution of glycol-borate which fills in the spaces between the corrugations and further iinprcgnates the cellophane.

The preferred electrolyte is that described in my Patent #l,891,207, comprising a viscous syrupy glycol-borate paste which is preferably made by dissolving ammonium borate and boric acid in hot ethylene glycol. For a more detailed description of the composition and manufacture of the paste, refence may be had to the patent. However, other viscous conductive electrolytes, including those formed by the reaction between one of the weak organic acids, such as citric, malic, lactic, tartaric, formic, phosphoric, their salts and one of the polyhydric alcohols of the classes glycols and glycerols, may be used.

In order to afford a. detailed description of some forms of the invention, reference is made to the accompanying drawing in which like numbers indicate like parts.

In the flat type condenser of Fig. 1, the anode (1) composed of aluminum having a pre-formed oxide film or layer is spaced from aluminum cathode (2) by cellophane sheet which has been rendered electrolytically conductive and tacky in the manner hereinabove described. sults, the cellophane itself, independent of the impregnating electrolyte, should have a thickness of approximately .002 or less.

In Fig. 2, the anode (1a) is similar to the anode (1) of Fig. 1, except that it is corrugated.

ln the rolled condenser of Fig. 3, an additional conductive cellophane spacer (30 has been provided.

In the housed condenser of Fig. i, the metal can acts as one terminal, being insulated from the other terminal (6) by insulator member Insulation at the lzggtom of the can is provided by insulator It is obvious that the construction shown in Fig. 4 may be used for dry or wet type condensers.

Since certain changes in carrying out the construction of the condenser and its components and obvious substitutions can be made in the materials used without departing from the scope of the invention, it is intended that all matters contained in the above description or shown in the accom- For best repanying drawing shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the eneric and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to all therebetween.

Having described my invention, what it claim as new and desire to secure by Let-- ters Patent, is:

1. An electrolytic condenser comprising two electrodes, one of which is film formed and a contacting conductive medium between the electrodes comprising a flexible nonfibrous cellulose sheet impregnated with a conductive electrolyte so as to afford a conductive path therethrough.

2. An electrolytic condenser comprising two electrodes, one of which is film formed and a contacting conductive medium spacing said electrodes comprising a flexible non-fibrous regenerated cellulose sheet impregnated with a conductive electrolyte so as to afi ord a conductive path thcrethrough.

3. An electrolytic condenser comprising two electrodes, one of which is film formed and a contacting conductive medium spacing said electrodes comprising a flexible nonfibrous cellulose sheet impregnated with an electrolyte composed of a compound containing a polyhydric alcohol of the classes comprising glycols and glycerols so as to afford a conductive path through said cellulose sheet.

l. [an electrolytic condenser comprising two electrodes, one of which is film formed and a contacting conductive medium spacing said electrodes comprising a flexible noniibrous cellulose sheet impregnated with a conductive composition containing a polyhydric alcohol of the classes comprising glycols and glycerols and a film maintaining electrolyte of one of the weak acids, boric, citric, malic, lactic, tartaric, formic and phosphoric with a salt of one of said acids suspended therein, said conductive composition afford ing a conductive path through said nonfibrous cellulose sheet.

5. An electrolytic condensercomprising two electrodes, one of which is film formed and a contacting conductive medium spacing said electrodes comprising a flexible non-tibrous cellulose sheet impregnated with an electrolyte containing a compound of a conductive salt with one of the polyhydric alcohols of the classes glycols and glycerols, said electrolyte affording a conductive path through said non-fibrous cellulose sheet.

6. An electrolytic condenser comprising two electrodes, one of which is film formed and a contacting conductive medium spacing said electrodes comprising a flexible noniibrous cellulose sheet impregnated with an one of which is corrugated and a contacting electrolyte of the classes comprising glycolborates and glycerol-borates so as to afiord a conductive path therethrough.

7. An electrolytic condenser com rising two electrodes, one of which is film ormed and acontacting conductive medium spacing said electrodes comprising a flexible nonfibrous cellulose sheet impregnated with a viscous organic electrolyte so as to afford a conductive path therethrough.

8. An electrolytic condenser comprising two electrodes, one of which is film formed and a contacting conductive medium spacing said electrodes comprising a flexible nonfibrous cellulose sheet of a thickness substantially not greater than -.002", impregnated with a conductive electrolyte so as to aflord a conductive path therethrough.

9. An electrolytic condenser comprising two electrodes, one of which is film formed,

conductive medium spacing said electrodes comprising a flexible non-fibrous cellulose.

sheet impregnated with a conductive electrolyte so as to afford a conductive path therethrough.

10. A conductive sheet spacer for electrolytic condensers comprising a flexible nonfibrous cellulose sheet material impregnated with a conductive electrolyte so as to afford a conductive path therethrough.

11. A conductive sheet spacer for electrolytic condensers comprising a flexible nonfibrous cellulose sheet material impregnated with an electrolyte composed of a compound containing a polyhydric alcohol of the classes comprising glycols and glycerols so as to afford a conductive path therethrough.

12. A conductive sheet spacer for electrolytic condensers comprising a flexible nonfibrous cellulose sheet material impregnated with a conductive composition containing a polyhydric alcohol of the classes comprislng glycols and glycerols, and a film maintaining electrolyte of one of the weak acids, boric, citric, malic, lactic, tartaric, formic and phosphoric with a salt of one of said acids suspended therein, said conductive composition affording a conductive path through said non-fibrous cellulose sheet.

13. A conductive sheet spacer for electrolytic condensers comprising a flexible nonfibrous cellulose sheet material impregnated with an electrol econtainin acom ound of a conductive sa t with one o the o yhydric alcohols of the classes glycols an glycerols, said electrol te affording a conductive path through sai non-fibrous cellulose sheet.

14. A conductive sheet spacer for electrolytic condensers comprising a flexible nonfibrous cellulose sheet material impregnated with an electrolyte of the class comprising glycol-borates and glycerol-borates so as to afford a conductive path therethrough.

15. A conductive sheet spacer for electrol tic condensers comprising a flexible nonbrous cellulose sheet material impregnated with a viscous organic electrolyte so as to afford a conductive path therethrough.

16. A conductive sheet spacer for electrolytic condensers comprising a flexible nonfibrous cellulose sheet of a thickness substantially not greater than .002, impre ated with a conductive electrolyte so as to afl drd a conductive path therethrough.

17. The method of making a conductive sheet spacer material for electrolytic condensers which comprises immersing a sheet of non-fibrous cellulose sheet in a conductive electrolyte and impregnating said sheet with said electrolyte so as to afford a conductive path therethrough.

18. The method of making a conductive sheet spacer-material for electrolytic condensers which comprises impregnating a sheet of non-fibrous regenerated cellulose sheet material with a viscous organic electrolyte so as to afford a conductive path therethrough.

19. The method of making aconductive sheet spacer material for electrolytic condensers which comprises impregnating a sheet of non-fibrous cellulose sheet material with an electrolyte of the classes com- SAMUEL RUBEN.

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